Method register

src/aria/private/utils/collection.ts:30–36

(item: T)

  });

  register(item: T) {
    this._items.update(set => {
      const newSet = new Set(set);
      newSet.add(item);
      return newSet;
    });
  }

  unregister(item: T) {
    this._items.update(set => {